Power field effect transistor is one of most i important transistors. The power field effect transistors mainly include two types: vertically diffused metal-oxide-semiconductor (VDMOS) transistor, and laterally diffused MOS (LDMOS) transistor. Compared to the VDMOS transistor, the LDMOS transistor has many advantages, such as better thermal stability and frequency stability, higher gain, lower feedback capacitance and thermal resistance, and constant input impedance.
However, such LDMOS transistor formed by existing techniques often cannot improve the hot carrier effect of the LDMOS transistor while adjusting threshold voltage of the LDMOS transistor, thus resulting in reduction of electrical performance of the LDMOS transistor. The disclosed device structures and methods are directed to solve one or more problems set forth above and other problems.